The present invention relates generally to exhaust treatment for an internal combustion engine and more particularly, but not exclusively, to a method, system, and software utilized to provide reductant to perform desulfurization (“de-SOx”) to regenerate a NOx adsorber.
The Environmental Protection Agency (“EPA”) is working aggressively to reduce pollution from new, heavy-duty diesel trucks and buses by requiring them to meet tougher emission standards that will make new heavy-duty vehicles up to 95% cleaner than older vehicles. Emission filters in the exhaust gas systems of internal combustion engines are used to remove unburned soot particles from the exhaust gas and to convert harmful pollutants such as hydrocarbons (“HC”), carbon monoxide (“CO”), oxides of nitrogen (“NOx”), and oxides of sulfur (“SOx”) into harmless gases.
Exhaust gas is passed through a catalytic converter that is typically located between the engine and the muffler. In operation, the exhaust gases pass over one or more large surface areas that may be coated with a particular type of catalyst. A catalyst is a material that causes a chemical reaction to proceed at a usually faster rate without becoming part of the reaction process. The catalyst is not changed during the reaction process but rather converts the harmful pollutants into substances or gases that are not harmful to the environment.
NOx storage catalyst units or adsorbers are used to purify exhaust gases of combustion engines. These NOx storage catalyst units, in addition to storing or trapping NOx, also trap and store unwanted SOx in the form of sulfates. The adsorption of SOx in the converter reduces the storage capacity of the adsorber and the catalytically active surface area of the catalyst. As such, NOx storage catalyst units must be regenerated to remove both NOx and SOx. The process of regenerating NOx adsorbers varies depending on whether operating in a de-NOx mode (in which NOx is converted and removed from the unit) or a de-SOx mode (in which the unit is ran through a de-SOx process). Accordingly, there is a need for methods, systems and software for controlling an engine to place a NOx adsorber through a de-SOx process.